Do Brook trout have personalities?

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Not all fish behave the same, according to a study published in a recent issue of the journal Animal Behaviour.

The study by Canadian scientists Alexander Wilson and Robert McLaughlin assessed whether the search tactics used by newly hatched Brook trout (Salvelinus fontinalis) represent behavioural syndromes.

Two different behavioural forms of newly hatched brook trout were identified in the field: those that were more active and those that were sedentary while searching for prey.

For the study, the authors first quantified the activity of individuals in the field, and then measuring their activity, water column use, and response to simulated risk from above in novel environment situations.

They tested whether active trout would take less time to escape from an erect glass jar placed in an aquarium and spend more time moving and in the upper part of the water column in an aquarium environment than sedentary trout.

The researchers then tested whether active trout would show more active escape behaviours in response to a simulated risk from above than would sedentary trout.

The results showed that active trout spent a higher proportion of time moving, spent less time near the aquarium bottom, and took less time to find their way out of an erect glass jar, on average, than did sedentary trout.

When presented with near-bank and open-water conditions over six days in the laboratory, active trout remained active and altered their activity less, on average, than sedentary trout. The researchers found no immediate correlation with field behaviour to responses to a pebble dropped in the aquarium (simulated risk from above).

Having demonstrated that recently emerged brook trout ...either differ in their propensity to move and use the water column at the time of emergence in ways that predispose them to adopt a sit-and-wait or active search tactic, or that very early experience, within a few weeks of emergence, quickly promotes and reinforces variation in the propensity to move and use the water column..., the authors conclude that they would ...expect evidence for behavioural syndromes to be subtle during the initial developmental and evolutionary stages of resource polymorphism and before the action of behavioural, physiological, morphological and ecological processes that might reinforce the correlations.

What we have uniquely demonstrated is that the raw material for such processes exists at a very early life stage in a population lacking distinct morphotypes.

This suggests that initial, individual differences in behaviour could have a more complex and important role in facilitating resource polymorphism than is currently recognized by hypotheses of diversification emphasizing the roles of chance, and of ecological conditions...

For more information, see the paper: Wilson ADM and RL McLaughlin (2007) Behavioural syndromes in brook charr, Salvelinus fontinalis: prey-search in the field corresponds with space use in novel laboratory situations. Animal Behaviour 74, pp. 689"698.